Variable capacity pump



Marh 8, 1960 J. M. RHOADES VARIABLE CAPACITY PUMP Filed March 8, 1956 M Mr 4 1 Z 7 m lv 0R n I I r E Z M .n 9 #NH 2 j w) w M I 0 \I a J w United States Patent VARIABLE CAPACITY PUMP John Merrill Rhoades, Waynesboro, Va., assignor to General Electric Company, a corporation of New York Application March 8, 1956, Serial No. 570,232

4 Claims. (Cl. 103--97) This invention relates to fluid pumps and more particularly to a centrifugal type of fluid pump.

Prior applications of the centrifugal type pump have not proved satisfactory where the flow requirements of the pump were to be varied over a wide range. In those appIications of the centrifugal pump where the variable flow is obtained through throttling or other methods of restricting the pump discharge, undue heating of the fluid being pumped has been encountered. In the variable flow applications where a speed regulation of the impeller is resorted to in order to vary the flow requirements, the pump efliciency has shown a decrease with low impeller speed. The use of centrifugal pumps whose pumping vane area is variable has contributed to a great extent in overcoming these difliculties while yet presenting further problems concerning the varying feature of the vanes and the necessary control for this feature. This invention is therefore directed to the elimination of these further problems.

Some of the many applications in which this invention may be suitably employed are: as a hydraulic power source for hydraulic servo-mechanisms, and in fuel systems including the main and reheat fuel system of turbojet engines.

An object of this invention is to provide an improved centrifugal pump of variable capacity.

Another object of this invention is to provide an improved centrifugal pump which may be adapted to be automatically variable in response to the pressure of the fluid being pumped.

A further object of this invention is to provide an improved variable capacity centrifugal pump which maintains substantially constant efliciency over a wide flow range.

Briefly stated, in accordance with one aspect of this invention, there is provided an impeller and a shroud arranged for rotation within a pump body and for axial movement one with respect to the other. The impeller and the shroud have radially projecting vanes on their opposed faces and the vanes of one are so formed to slidingly receive a part of the vanes of the other. Rotation of the impeller and shroud causes fluid to flow due to the action of the vanes on the fluid, and axial movement therebetween varies the effective pumping vane area to'change the pump capacity.

This invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Figure l is a cross sectional view of the pump showing a combined impeller and shroud vane with the pumping area at a maximum.

Figure 2 shows the pumping vane area reduced for a low flow range.

Figure 3 is a cross section of a combined impeller and shroud vane taken along the line 33 in Figure 1.

Referring to Figure l of this invention, 1 and 2 are complementary sections which together form the pump 7 2,927,536 Patented Mar. 8, 19.60

body. For assembly purposes, circumferential flanges 3 and 4 having holes 5 therein are provided on the sections 1 and 2 respectively. Bolts 6 extend through the holes 5 to engage nuts 7 to maintain the assembled relationship. In the assembled position, the cooperation of the sections 1 and 2 forms a peripheral manifold 8 which receives the fluid being pumped directly from the impeller.

Projecting axially from the outer face of section 2 is a relatively short pipe-like extension 9. An annular member 10 is positioned within the extension 9 in concentric relationship, with a portion of the outside surface of the member 10 being spaced from the inner surface of the pipe-like extension 9. The concentric mounting and spacing of the surfaces of the annular member 10 and pipe-like extension 9 forms an annular chamberor recess 11 therebetween. Member 10 may be sealed to extension 9 or the annular member may be formed within the extension as an integral part thereof, such as by casting the section as a whole or by machining the annular recess 11, or alternately by welding the annular member 10 in its final position to the extension 9.

Mounted for rotation within the pump body is an impeller 12 which is of a well-known type comprising generally a web section 13 with radially extending vanes 14 projecting from its face. In order to vary the capacity of the impeller 12, there is provided a shroud 15 which is spaced axially from the impeller 12. Provision is made to support the shroud 15 for both rotational and axial sliding movement by having a cylindrical projection 16 formed concentrically thereon which extends into the annular recess 11 in axial sliding relationship. The annular member 10 performs the combined functions of acting as a cylindrical wall member for axial movement of the shroud 15 and as a bearing for supporting the shroud 15 for rotation thereon.

From the face of the shroud 15 radially extending vanes 17 project in a direction toward the projecting impeller vanes 14. The shroud vanes 17 are formed with a channel or groove 18 in their free radial edges which face the impeller, for slidably receiving the corresponding edges of the impeller vanes 14 in what may be described as a tongue and groove relationship. While Figure 3 shows this tongue and groove relationship in singular form between a shroud vane and an impeller vane, it is to be understood that there may be a plurality of grooves formed in each shroud vane and a corresponding plurality of tongues formed in each impeller vane. The tongue and groove relationship performs the dual function of allowing axial movement of the shroud 15 and also transmitting the driving force of the impeller 12 to the shroud 15 for rotation thereof. Movement of the shroud 15 towards the impeller 12 results in the tongues or edges of the impeller vanes 14 progressing further into the grooves 18 of the shroud vanes 17, thus reducing the combined area of the impeller vanes 14 and the cooperating shroud vanes 17. This reduction in vane area effectively reduces the capacity of the pump. Conversely, a movement of the shroud 15 away from the impeller 12 results in less penetration of the edges of impeller vanes 14 within grooves 18, thus increasing the combined area of the impeller vanes 14 and the cooperating shroud vanes 17 and thereby increasing the pump capacity.

The capacity of the pump thus far described is varied by changing the pumping area of the combined impeller vanes 14 and shroud vanes 17. With this change in pumping area, a greater or lesser fluid flow enters the manifold 8, thus presenting problems of fluid flow fluctuations or time lag in the flow requirement. These problems are effectively minimized by forming on shroud 15 an annular wall portion 19 which extends into the manifold 8 and -is shaped to conform to the side wall configuration of the "manifold 8. Upon an axial movement of shroud 15, the annular wall portion 19 is also moved axially in order to change the active volume of the manifold 8 to correspond to the fluid flow.

' A favora'ble advantage of the tongue and groove rela= tio'ns'hip resides in its function of holding to a minimum any leakage of fluid through the combined impeller and shroud vanes while permitting axial movement for vary* ing the pumping vane area. The tongue and groove relationship is further advantageous in transmitting the driving force of the impeller 12 to the shroud 15 which precludes the necessity of fixing the shroud 15 to the impeller 12 or to the impeller shaft by keying or other means.

In order to bias the shroud 15 in one direction, springs 20 are disposed within the grooves 18 of the shroud vanes 11 to bear against the impeller and thus bias the shroud axially. Figure 1 shows springs 20 employed to bias shroud 15 away from impeller 12 to thus present a maximum of combined vane area to the fluid being pumped. In the particular form of this invention as disclosed, the shroud 15 is axially slidable; however, the impeller 12 may be "mounted to be axially slidabl'e and the shroud 15 remain fixed, or alternatively, both the impeller 12 and'th'e shroud 15 may be axially slidable.

I To vary the capacity of the pump by axial movement of the shroud 15, fluid under pressure is introduced into the annular space 11 through a passage 21 which is drilled or otherwise provided in the pipe-like extension 9. The fluid in the annular space 11 then exerts pressure on the piston face 22 of the cylindrical projection 16, and depending on the degree of pressure involved, serves to move shroud 15 axially against the biasing force of the springs 26. The pressure fluid employed may be one of many available hydraulic fluids and obtained from any suitable pressure source other than the pump itself. "If, however, the manifold 8 or the discharge side of the pump is made available as a source of fluid under pres- Sure, the pump may be made self-regulating.

The self-regulating type of control not only eliminates the need of a special control fluid and the necessary equipment to make up that control, but also provides a simple and convenient regulating arrangement adaptable to various conditions and applications.

Self-regulation is accomplished by the employment of springs 28 of which the aggregate biasing force is properly related to the pressure of the control fluid from the pum discharge. Consideration may, therefore, be given not only to the biasing force of the springs 20 but also to the number of such springs employed. If the number of springs 20 is varied, the biasing force should be evenly disposed circumferentially of the shroud. With this arr'angement, fluid pressure acts on the piston face '22 of the cylindrical projection 16 to overcome the biasing action of the springs 20 and move shroud 15 to a position of less pumping vane area. While the described embodiment of this invention employs fluid pressure as the control means, it is to be understood that other means ineluding mechanical and electrical devices may be employed with good results.

The operation of this pump is as follows: The pipe-like extension 9 is connected to a source of fluid and the impeller 12 is then rotated. Fluid is forced to flow, as shownby the arrows in Figure 1, between theshroud 15 and impeller 12, due to the action on the fluid by the shroud and impeller vanes 17 and 14 respectively. From the vanes the fluid is received by the manifold 8 for delivery to the pump outlet. Control fluid is introduced into the annular space 11 to move the shroud 15 in an axial direction. This movement is accomplished through the aforementioned tongue and groove relationship and takes place against the biasing action of the springs 20. A movement :of the shroud 15 towards impeller 12 reduces the eflectivepumping area of the vanes therebe sw at. convers ly, a sed c ion in the control pressure allows the springs 20 to bias the shroud 15 away from the impeller 12 which increases the pumping area of the vanes.

With the self-regulating arrangement, the control pressure becomes variable through throttling of the pump discharge. The throttling or other restriction of free flow at the pump outlet-or beyond creates a pressure increase in the manifold 8. This increase in pressure may then be transmitted in any suitable manner through passage 21 to the annular space 11 to act on the piston face 22 of the cylindrical projection 16. The pump'then becomes self-regulating in that the shroud member is moved axially in response to pump discharge pressure to vary the pumping'area of the vanes between the shroud and the impeller and therefore the capacity of the pump.

It is to be understood that this invention is not limited to any specific form or arrangement of parts except inso' far as such limitations are specified by the claims.

What is claimed is: 1. In a variable capacity centrifugal pump, the combination comprising, a pump body, a manifold encircling said body, an impeller mounted for rotation within said body and including radially extending vanes projecting from the face thereof, a shroud spaced from said impeller in axial sliding relationship thereto, radially extending vanes projecting from the face of said shroud, said shroud vanes having grooves in their radial free edges, said impeller vanes being slidingly received in said grooves, and means for moving said shroud axially to vary the pumping vane area between said impeller and said shroud.

2. In a variable capacity centrifugal pump, the combination comprising, a pump body, a manifold encircling said body, an impeller mounted for rotation within said body and including radially extending vanes projecting from the face thereof, a shroud spaced axially from said impeller, radially extending vanes projecting from the face of said shroud, said impeller and said shroud being so mounted to provide relative axial motion therebetween, said shroud vanes having grooves in their radial free edges, said impeller vanes being slidingly received in said grooves, and biasing means residing within at least one of said grooves to provide a biasing force between said shroud and said impeller. 3. In a variable capacity centrifugal pump, the combination comprising, a pump body, an external pipe-like extension carried by said body and having an internal annular recess therein, a manifold encircling said body, an impeller mounted for rotation within said body and including radially extending vanes projecting from the face thereof, a shroud spaced axially from said impeller in sliding relationship thereto, radially extending vanes projecting from the face of said shroud, said shroud vanes and said impeller vanes being so formed that a part of one is slidingly received within the other, a cylindrical projection carried by said shroud and extending into said annular recess to define therewith an expansible chamber motor means, and means for applying a hydraulic fluid under pressure to said motor means to effect movement of said shroud. v

4. In a variable capacity centrifugal pump, the combination comprising a pump body including an encircling manifold, an impeller mounted for rotation within said body and including radially extending vanes projecting from the face thereof, a shroud spaced axially from said impeller in sliding relationship thereto, radially extending vanes projecting from the face of said shroud, said shroud vanes and said impeller vanes being so formed that a part of one is slidingly received within the other, a first tubular member carried by said shroud to provide an inlet flow passage to the space between said impeller and said shroud, a second tubular member carried by said pump body in surrounding concentric relationship to said first tubular member, bearing surfaces on radially opposed portions of said tubular members providing journal means for said shroud, and means for cfiecting 6 Green Feb. 15, 1944 Stepanofi Sept. 19, 1944 FOREIGN PATENTS Great Britain Feb. 12, 1943 France Jan. 13, 1925 France Aug. 30, 1950 

